linux-kernel - Re: [PATCH 07/12] time: Try to catch clocksource delta underflows

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:	Sat, 7 Mar 2015 10:34:35 +0100
From:	Ingo Molnar <mingo@...nel.org>
To:	John Stultz <john.stultz@...aro.org>
Cc:	lkml <linux-kernel@...r.kernel.org>,
	Dave Jones <davej@...emonkey.org.uk>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Richard Cochran <richardcochran@...il.com>,
	Prarit Bhargava <prarit@...hat.com>,
	Stephen Boyd <sboyd@...eaurora.org>,
	Peter Zijlstra <peterz@...radead.org>
Subject: Re: [PATCH 07/12] time: Try to catch clocksource delta underflows


* John Stultz <john.stultz@...aro.org> wrote:

> In the case where there is a broken clocksource
> where there are multiple actual clocks that
> aren't perfectly aligned, we may see small "negative"
> deltas when we subtract now from cycle_last.

So this is a typical example where putting argument references is 
really helpful. Consider these two variants:

   deltas when we subtract now from cycle_last.

   deltas when we subtract 'now' from 'cycle_last'.

I had to read the first variant three times until I realized that 
'now' is a C variable misleadingly inserted into English text.

> The values are actually negative with respect to the
> clocksource mask value, not necessarily negative
> if cast to a s64, but we can check by checking the
> delta see if it is a small (relative to the mask)
> negative value (again negative relative to the mask).

typo.

Thanks,

	Ingo
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/